SOURCE

// Input:
// 26

// Output:
// "1a"
// Input:
// -1

// Output:
// "ffffffff"
//使用js自带方法
//return (num>>>0).toString(16);
//不使用
    var toHex = function(num) {
        var arr = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'];
        var s = (num >>> 0).toString(2),
            ss = '';
        for (var i = s.length; i > 0; i -= 4) {
            ss = arr[parseInt(s.substring(i - 4, i), 2)] + ss;
            //console.log(ss)
        }
        return ss;
    };
    console.log(toHex(26));
    console.log(toHex(-26));
    console.log(toHex(-1));